Treatment of tar



ay 1.2, 1935 f s. P. MILLER 2,040,101

' TREATMENT 0F TAR Filed Aug. V5, 1952 ATTO R N EY Patented May 12, 1936 UNITED STATES PATENT OFFICE TREATMENT F TAR Application August 5, 1932, Serial No. 627,658

18 Claims.

'I'his invention relates to an improved process for the selective distillation and recovery of tar acids from tar, etc., whereby the tar acids can be recovered directly from the tar instead of from distillate oils produced from the tar. The invention also includes an improved process of recovering tar acids from tarry oils or from tar distillates containing tar acids together with similar boiling and higher boiling constituents.

The invention also includes an improved method for the treatment of Wet tar containing phenols or tar acids for the production therefrom of dehydrated and dephenolized tar and of tar acids.

The common method of recovering tar acids or phenols from tar is to distill the tar to produce distillate oils and to extract the tar acids from the distllates with a caustic soda solution. A large amount of distillate must be handled in most cases to produce a relatively small amount of tar acids. Where the tar acids are extracted from the distillates at a plant remote from the tar distillation plant the cost of transportation of the distillate oil is an added expense. Tar acids cannot be directly extracted from tar with caustic soda solutions in a commercially satisfactory manner by methods now known.

The present invention overcomes the objections to prior processes, such as those above mentioned, and enables phenols or tar acids to be readily produced in a simple and advantageous manner directly from the tar or tarry oil, etc.

According to one embodiment of the present invention the tar which is subjected to the deacidiiying or dephenolizing treatment is freed from water and from a considerable part of the lower boiling oils and is heated to a temperature considerably above the boiling point of Water and preferably above the initial boiling point of tar, e. g., to temperatures around 125 to 200 C., and there are circulated through the tar at these elevated temperatures vapors of hydrocarbon constituents of the tar to eiect a selective distillation of tar acids from the tar; the resulting vapors are then passed through a suitable absorber, such as a caustic soda absorber, maintained at such temperature and with such a high concentration of caustic that a highly concentrated carbolate solution is directly produced.

The tar produced by the destructive distillation or carbonization of coal, etc. usually contains more or less water admixed therewith, this water being produced during the destructive distillation or being introduced into the gases to assist in separating the tar therefrom. Even after the tar is permitted to settle and the greater part of the water removed by sedimentation, the tar still contains small percentages of water, frequently in the range of 2-3% or less and sometimes amounting to as much as 5 or 10% or more of the tar. 6 The dehydration of such Water-containing tar can advantageously be combined with the selective distillation and recovery of tar acids from the dehydrated tar so that a dehydrated and more or less dephenolized refined tar or low melting point pitch is directly produced.

In carrying out the invention with Water-containing tar by the preferred procedure, the tar is preheated in a continuous manner to a temperature considerably above the boiling point of water and preferably above the initial boiling point of the tar so that the water and lower boiling constituents of the tar are converted into vapors; the resulting vapors are then drawn off from the preheated and dehydrated tar and recirculated into intimate Contact with the tar and also circulated into contact with a hot alkaline solution, such as a caustic soda solution, to absorb the phenols or tar acids and separate them from the circulating vapors without removal of vapors of other constituents of the tar in amount in excess of that soluble in the carbolate solution resulting from the absorption of the tar acid vapors in the hot alkaline solution, before the unabsorbed vapors return for recirculation in contact with the preheated tar. In conjunction with such recirculation and continuous introduction of Water vapor and oil vapors into the recirculating vapors, there is drawn oir" from the recirculating vapors an amount or" steam and hydrocarbon oil vapors similar to the volume introduced into the cycle by the continuous supply of steam and oil vapors from the preheating and initial distillation of the tar.

When tar is dehydrated and heated considerably above the boiling point of Water and above the initial boiling point of the tar, e. g., to temperatures around 125 C. or higher, the tar acids can readily be distillated from the uid tar in a selective manner by recirculating therethrough hydrocarbon oil vapors which prevent or retard the distillation from the tar of neutral oils of similar boiling points to those of the tar acids removed. Thus while tar is dephenolized with difliculty at temperatures around C., it is easily dephenolized at temperatures around, e. g. C. or higher. At temperatures around 100 C., an excessive amount of inert gas must be recirculated, but it is possible at temperatures of around 125 C. or above to eiect commercially satisfactory removal of tar acids. For example, at 150 C. or higher it is possible to eiect removal of the greater part of the tar acids from the tar with the recirculation of around 250 cubic eet of vapors per gallon of tar, and it is possible moreover to recover the phenols in the form of a carbolate solution containing upwards of 50% of tar acids depending on the tar acid content of the tar being treated.

The present invention is of more or less general application to the dehydrating and dephenolizing of wet tars or tarry oils of various kinds produced from the distillation of coal at various coke oven, gas retort or low temperature distillation plants, etc. It is also applicable to the dehydration and dephenolizing of tarry oils such as the lighter tars produced in the second stage of condensation in the condensers at coke oven plants or gas retort plants. It is also applicable to the treatment of phenol-containing distillates such as carbolic oils or creosote oils which contain phenols together with similar boiling and higher boiling constituents. Where the tar, etc. is a wet tar the dehydration is, as above pointed out, advantageously combined with the dephenolizing, with utilization of the steam and oil vapors resulting from the dehydration and distillation for the dephenolizing of the dehydrated tar.

Wet tars can, however, be independently dehydrated before subjecting them to the process and in that case the dehydrated tar, or partially distilled tar, is heated to a similar high temperature, considerably above the boiling point of water, e. g., around C. or higher, and is maintained at such high temperature and in a fluid state during the passage of the hydrocarbon vapors therethrough to effect selective distillation 0I" tar acids therefrom. Tar products which are initially produced in a dry condition may likewise be dephenolized in accordance with my process as outlined above.

The vapors which are recirculated through the highly heated and fluid tar are hydrocarbon vapors, or they contain hydrocarbon vapors admixed with other vapors, such as steam, or with other vapors or gases. The steam resulting from the preliminary dehydration and partial distillation of the tar is advantageously used in the process, together with the low boiling hydrocarbon vapors produced by such initial dehydration and distillation. Some distillation of neutral oils may take place during the dephenolizing treatment, but such distillation will ordinarily be relatively small in amount and the tar acids will be selectively distilled, leaving behind the greater part of the neutral oils of similar boiling point.

The product produced by the dephenolizing treatment of the present invention will be a rened or partially distilled tar. It will be freed not only from any water contained in the raw tar but also from lower boiling oils which are removed during the preliminary dehydration and distillation. This preliminary distillation can advantageously be carried to the point of distilling sucient low boiling oils to give diectly a pitch of low melting point suitable for use for example for road making or road treating purposes. It will also be freed from a large part of its tar acids.

The caustic soda absorber is also operated at a high temperature. While temperatures as low as 120 C. will give carbolate solutions containing around 40 to 50% tar acids, higher temperatures can advantageously vbe used and carbolate solutions of even higher tar acid content, up to around 60 or 70% or higher can be produced. The limiting upper temperature is the temperature at which the carbolate solution will remain sufliciently liquid to be handled. At temperatures around to 160 C. carbolate solutions can be produced containing around 60% or higher of tar acids.

It is not necessary that the temperature of the carbolate solution and of the hot tar being dephenolized should be the same, and either the carbolate solution or the tar can be heated. In continuous operations, however, there are advantages in preheating the tar to a high temperature, e. g., around 200 C. or even up to around 250 C. to effect dehydration and partial distillation and then to maintain the dehydrated tar undergoing dephenolization and also the caustic absorber at temperatures around 140 to 150 C. In this way the entire amount of heat required for carrying on the process is supplied to the tar during the pre-heating and dehydrating treatment and since the tar undergoing dephenolization and the caustic solution in the absorber then will be at substantially the same temperature, there will be substantially no condensation of neutral oil vapors in the caustic solution to remove from the circulating vapors and gases an amount of neutral oils in excess of that soluble in the resulting carbolate solution.

The process can be carried out in diierent types of apparatus. The dehydration and dephenolizing of the tar can be carried out as a batch operation or as a continuous operation. One form of apparatus which has been found particularly advantageous for preheating the tar and supplying heat to the process is a pipe coil still which discharges into a vapor separating chamber at a temperature such that the resulting dehydrated and partially distilled tar is at a suitably high temperature for the dephenolizlng treatment and the steam and hydrocarbon vapors at a suitable temperature to mix with the circulating vapors.

While it is possible, by the present process, to remove most if not all of the tar acids from the tar, it may be more advantageous to remove only the lower boiling point tar acids which constitute for many purposes the more valuable tar acids and which may form up to around 70 or 80% of the total tar acid content of the tar. The lighter tar or tarry oils recovered in the condensers of coke oven plants and which may represent only a quarter to a third of the total tar may nevertheless contain the greater portion of the tar acids and particularly the lower boiling tar acids which can be more readily removed; and these tarry oils can be separately treated by the present process for the recovery of such tar acids therefrom.

The present process can be carried out in connection with the further distillation of the tar. That is, the dephenolized tar which has already been freed from water and lower boiling constituents and from a large part of its tar acids can be further distilled to produce pitches of intermediate or higher melting points and distillate oils, and the distillate oils produced will be free from or low in tar acid content.

The invention will be further described in connection with the accompanying drawing which illustrates, in a more or less conventional and diagrammatic manner, suitable apparatus for the practice of the invention, but it will be understood that the invention is not limited thereto.

In the accompanying drawing, Figure 1 shows one form of apparatus for carrying out the process; and

Figure 2 is a diagram showing the cyclic nature of the process for continuous supply of tar, etc., and continuous removal of vapors, etc.

The apparatus illustrated is suitable for the treatment of wet tar to eiect dehydration and partial distillation as well as dephenolizing of the resulting highly heated tar.

Referring to Fig. l, wet tar, such as coal tar from a by-product coke oven plant, containing several percent of tar acids, is supplied from the storage tank I by means of pump 2 and line 3 to a preheating coil 4 arranged in a heating furnace or chamber 5 heated by high temperature steam, or by waste nue gases, or by a separate burner or combustion chamber, or otherwise. From the preheating coil, the preheated tar passes through line 6 to the top of the dephenolizing tower or scrubber 'I shown as a tall packed tower which provides for intimate contact of the tar iowing downwardly therethrough and the vapors passing upwardly therethrough, the packed section of the tower being indicated at 9. The steam and oil vapors evolved in preheating the tar entering the dephenolizing tower through the line 6 with the preheated liquid tar and are introduced into contact with the stream of gas passing through the tower. The steam and oil vapors evolved in preheating the tar mix with the vapors leaving the top of the tower and pass through the line I4 to the bottom of the caustic scrubber I5.

The recirculating vapors are supplied to the bottom of the dephenolizing tower 'I' by pump IB through line II and pass upwardly countercurrent to the downwardly iiowing tar, the vapors at the top of the tower admixing with those discharged frorn the preheating coil 6 and passing through pipe I4 to the caustic scrubber I5. The tar, dehydrated and more or less dephenolized, escapes from the bottom of the dephenolizing tower through line S to a place of storage or use for further treatment. The high temperature of this dehydrated and dephenolized tar adapts it vfor use for preheating the raw wet tar in a heat interchanger and for other purposes.

The caustic scrubber i5 is shown as a packed tower to which fresh caustic solution may be supplied through line I'I and from which carbolate solution can be withdrawn through line I8 to receptacle I9. The tower is provided with means for recirculating the caustic and carbolate solution, comprising the recirculating line 2B having pump 2I therein and discharge nozzle 29 for distributing the recirculated solution over the top of the packed section of the tower. A heat interchanger 23 for supply or removal of heat is shown in case it desired to heat the recirculating carbolate and caustic solution to maintain it at the desired temperature, or in case it is desired to cool the solution somewhat, as in case the temperature of the recirculating vapors is so high, due to the high temperature at which the tar is supplied, that cooling is required to avoid too high a concentration oi the caustic and carbolate solution. The excess of steam and neutral oil vapors is drawn off continuously through the line 24 to a condenser (not shown).

The dephenolizing tower and the caustic scrubber, as well as the connecting line, should be heavily insulated to keep down heat losses and to assist in maintaining uniform conditions of operation when desired.

The cyclic nature of the process, with the substances continuously supplied and removed, is

illustrated diagrammatically in Fig. 2. The wet tar is preheated and enters the cycle at the dephenolizer where the steam and oil vapors produced by the preheating operation join with the circulating stream and pass to the caustic scrubber in which the tar acids or phenol vapors are combined, and from which the steam and oil vapors return to the dephenolizer, the excess steam and neutral oil vapors being drawn off between the caustic scrubber and the dephenolizer. A vent for this purpose may be provided in the circulating vapor line either following the caustic scrubber or ahead of the caustic scrubber. In the latter case, where the excess steam and neutral oil vapors are drawn from the circulating system ahead oi the caustic scrubber, these vapors will be accompanied by tar acid vapors. Caustic solution is supplied to the caustic scrubber and carbolate solution is withdrawn. The dehydrated and partially phenolized tar is withdrawn from the dephenolizer.

The cycle is one in which neutral oil vapors, and steam when wet tar is being treated, are continuously supplied from the preheating operation, in which preheated tar is also supplied by the preheating operation, in which tar acid or phenol vapors are removed from the tar in the dephenolizer by the recirculating vapors, and in which the tar acid vapors are continuously removed from the recirculating vapors in the caustic scrubber. The caustic solution may be recirculated, as illustrated in Fig. l, and where a dilute caustic solution is supplied and high temperature steam and oil vapors are recirculated, the caustic will be concentrated. Some condensation of neutral oils may occur in the caustic scrubber. For the most part, however, the steam and neutral oil vapors will be recirculated, and only such amount thereof will be withdrawn as corresponds to the amount being continually supplied by the preheating operation.

In general, the rate of supply of the preheated tar is such that the volume of steam and oil vapors supplied continuously by the preheating operation will be but a small part of the volume of recirculating steam and oil vapors, and the amount that will be Withdrawn continuously from the cycle will also be a small part of the total volume of recirculating vapors.

If the tar is preheated to a temperature above that of the boiling point of any of the phenols. relatively rapid 4distillation of the phenols will occur, but the process can be carried out without heating Yof the tar to the normal boiling point of the phenols since the tar can be readily dephenolized at temperatures considerably below the boiling point of even phenol itself by subjecting it repeatedly to contact with the steam and neutral oil vapors in a dephenolizing scrubber.

In starting the process, the tar advantageously preheated to a temperature of to 200 C. is admitted to the tower. The steam and vapors produced by the preheating operation rapidly sweep the gas out of the apparatus and there is quickly built up a mixture or" steam and neutral oil vapors that is subsequently recycled throughout the operation. The recirculating vapors will establish o-r tend to establish equilibrium so that the removal of tar acid vapors from` the tar will be accomplished without the removal of neutral oil vapors in as large amount as occurs in the usual methods of distilli'ng tar for recovery of tar acids. As a result, the dehydrated and partly dephenolized tar will contain the greater part if not all of the neutral oil vapors corresponding in boiling point range to the tar acids removed. Under certain conditions of operation the ratio of steam to neutral oil vapors in the recirculating vapors may be, for example, as 85 to 15, that is, 85% steam and 15% oil vapors, by volume. With any given tar, the ratio of oil vapors to steam will increase with increasing temperatures. By maintaining the temperature of the recirculating vapors, considerably above the boiling point of water, not only is the tar maintained in a dehydrated state and lower boiling phenols rapidly removed, but the caustic and carbolate solution will tend to establish and maintain equilibrium with the high temperature recirculating gases so that a carbolate or high concentration will be obtained.

The volume rate of recirculating vapors will vary somewhat, particularly with respect to the temperature of preheating the tar, with the type or" tar acids present and also with the tar acid content of the tar. With coke oven tar containing around 3 to 5% tar acids and with preheating of the tar to temperatures in excess of about 125 C. the volume of vapors recirculated per gallon of tar dephenolized will ordinarily be less than 350 cubic feet to obtain a recovery of upwards of 50% of the tar acid content of the tar; and, with higher degrees of preheating oi the tar, for example up to around 150 to 200 C., an increased percentage of tar acids can be recovered with an even lower volume of vapors recirculated per gallon of tar dephenolized.

In general the circulation of a given volume of inert gas will remove an approximately xed amount of tar acids from average commercial tars under given temperature conditions. If a given percentage recovery of the tar acids contained in the tar is desired, more inert gas must be circulated per gallon of tar in the case of rich tar-acid tars than in the case of tars low in tar acids.

As illustrative of the size of the apparatus required, a plant for dephenolizing 40,000 gallons of tar per day with a rate of vapor recirculation of about 215 cubic feet per gallon of tar may have a dephenolizing tower of about 42 inches in diameter and a caustic so-da scrubber about 42 inches in diameter, with vapor circulating lines of about 18 inches in diameter and a blower adapted to circulate about 6,000 cubic feet of vapors per minute. Such a plant, with the tar preheated to a temperature between 150 and 200 C. and with the temperature of the carbolate solution at around 150 C. will readily remove upwards of one-half of the tar acids contained in the tar, when the tar has between 3 and 5% tar acid content. Such a plant can be operated with preheating of the tar, all of the heat required for the process being supplied through the preheating of the tar, the hot tar being relied upon to preheat the circulating vapors and these vapors in turn heating the, carbolate solution.

For example, in apparatus of the type illustrated in Fig. 1, 66.1% of the tar acids were removed rom tar which contained 3.8% of tar acids under the following operating conditions: 1400 gallons of tar were fed to the dephenolizing tower per hour and the gas was recirculated through the system by the blower l at the rate of 5900 cubic feet per minute, or the equivalent of about 252 cubic feet of gas per gallon of tar treated. The tar was preheated to 199 C. in a preheater and ashed into the dephenolizing tower. The recirculated gas entered the bottom of the dephenolizing tower at approximately 188 C. The caustic used contained about 50% NaOH. The temperature of the recirculated carbolate was 184 C. The carbolate formed was withdrawn from the bottom of the extractor and contained 65.4% of tar acids. The steam and neutral oil vapors bled from the recirculating system were cooled in a condenser. The neutral oil recovered in this manner represented about 0.9% of the tar treated; This oil contained 3.6% of tar acids or about 0.9% of the acid removed from the tar. The acid recovered as carbolate was calculated to be 65.2% of the total acid present. The percent of tar acids left in the treated tar withdrawn from the dephenolizing tower was calculated to be 33.9%.

In a diierent run in other apparatus using a somewhat lower gas temperature and a higher rate of recirculation of the gas through the system 74.8% of the acids present in the tar were recovered as carbolate; the percent of tar acid recovered in the oil condensed from the gas and vapors bled from the system was 0.5% of the tar acids in the tar and 24.7%. were left in the tar withdrawn from the bottom of the dephenolizing tower. 306 cubic feet of gas were recirculated per gallon of tar treated. The gas and vapor left the top of the dephenolizing tower at 150 C. 4.9% of the tar was recovered as neutral oil condensed from the bleed.

It will thus be seen that the present invention provides an improved process for the dephenolizing of tar, or for the dehydration and dephenolizing of tar, in which the tar is heated to a temperature considerably above the boiling point of water and in which the hot and thinly uid tar is subjected to a selective distillation of tar acids which are recovered directly without the distillation of a large amount of neutral oils and in which a refined tar or low melting point pitch is also produced as a separate product or which can be further distilled to give distillate oils and higher melting point pitches.

It will further be seen that the improved process has many advantages, among which may be mentioned the direct production of a strong carbolate solution of high tar acid content, the compact nature and size of the equipment required and, in the case of the continuous process, the continuous dehydration and preheating of the tar and its supply to the cyclic process, the utilization of the water vapor and neutral oil vapors produced by the dehydrating and preheating operation in the cyclic process, the rapid dephenolizing of the tar, etc. The process of my invention while described above primarily for operation at atmospheric pressure may be operated at subatmospheric pressure or pressure above atmospheric if desired.

The word tar" as used in this specication is intended to mean raw tar, topped tar, dehydrated tar or partially distilled tar.

Having now particularly described the nature of my invention and in what manner the same is to be performed, I declare that what I claim is:

1. The method of selectively recovering tar acids from tar, which comprises bringing tar containing tar acids and an inert gas containing vapors of constituents of said tar other than tar acids into intimate contact with each other at a temperature of about 125 C. or higher to eiect selective vaporization of tar acids from the tar, and passing admixed gases and vapors (including tar acid vapors) resulting from the treatment of the tar into intimate contact with a hot alkaline solution at a temperature at which the tar acid vapors are selectively removed from the admixed gases and vapors without removal of vapors of other constituents of the tar in amount in excess of that soluble in the carbolate solution resulting from the absorption of the tar acid vapors in said hot alkaline solution.

2. The method of selectively recovering tar acids from tar, which comprises bringing tar containing tar acids and an inert gas containing vapors of constituents of said tar other than tar acids into intimate contact with each other at a temperature of about 125 C. or higher to eiect selective vaporization of tar acids from the tar, passing admixed gases and vapors (including tar acid vapors) resulting from the treatment of the tar into intimate contact with a hot alkaline solution, recycling into contact with the tar inert gas and vapors unabsorbed by said alkaline solution and maintaining said inert gas and vapors throughout their circulation in contact with the tar and the hot alkaline solution and return to renewed contact with the tar, at elevated temperatures at which the tar acid vapors are selectively removed from the circulating gas and vapors by the alkaline solution without removal therefrom of vapors of other constituents of the tar in amount in excess of that soluble in the carbolate solution resulting from the absorption of the tar acid vapors in said hot alkaline solution.

3. The method of selectively recovering tar acids from tar which comprises contacting tar containing tar acids at a temperature of about 125 C. or higher with inert gas containing vapors of constituents of said tar other than tar acids to eifect selective vaporization of tar acids from the tar, and passing admixed gas and vapors (including tar acid vapors) resulting from the treatment of the tar into contact with a hot alkaline solution at a temperature of about C. or higher to absorb selectively the tar acid vapors.

4. The method of selectively recovering tar acids from tar which comprises contacting tar containing tar acids at a temperature of about C. or higher with an inert gas containing vapors of constituents of said tar other than tar acids to effect selective vaporization of tar acids from the tar, passing admiXed gas and vapors (including tar acid vapors) resulting from the treatment of the tar into contact with a hot alkaline solution at a temperature of about 120 C. or higher to absorb selectively the tar acid vapors, and recycling into contact with the tar inert gas and vapors unabsorbed by said alkaline solution.

5. The method of selectively recovering tar acids from tar, which comprises bringing tar containing tar acids and an inert gas containing vapors of constituents of said tar other than tar acids into intimate contact with each other at a temperature between about 125 and about 200 C. to eiect selective vaporization of tar acids from the tar and passing admixed gases and vapors (including tar acid vapors) resulting from the treatment of the tar into intimate contact with a hot alkaline solution at a temperature at which the tar acid vapors are selectively removed from the admixed gases and vapors without removal of vapors of other constituents of the tar in amount in excess that soluble in the carbolate solution resulting from the absorption of the tar acid vapors in said hot alkaline solution.

6. The method of selectively recovering tar acids from tar, which comprises bringing tar containing tar acids and an inert gas containing vapors of constituents of said tar other than tar acids into intimate contact with each other at a temperature between about 125 and about 200 C. to eiTect selective vaporization of tar acids from the tar, passing admiXed gases and vapors (including tar acid vapors) resulting from the treatment of the tar into intimate Contact with a hot alkaline solution at a temperature at which the tar acid vapors are selectively removed from the admixed gases and vapors without removal of vapors of other constituents of the tar in amount in excess of that soluble in the carbolate solution resulting from the absorption of the tar acid vapors in said hot alkaline solution and recycling into contact with the tar inert gas and vapors unabsorbed by said alkaline solution.

'7. The method of selectively recovering tar acids from tar, which comprises contacting tar containing tar acids at a temperature between about 125 and about 200 C. with an inert gas containing vapors of constituents of said tar other than tar acids to effect selective vaporization of tar acids from the tar, and passing admixed gas and vapors (including tar acid vapors) resulting from the treatment of the tar into contact with hot alkaline solution at substantially the same temperature as that at which the said tar and inert gas are contacted to absorb selectively the tar acid vapors.

8. 'I'he method of selectively recovering tar acids from tar, which comprises contacting tar containing tar acids at a temperature between 125 and about 200 C. with an inert gas containing vapors of constituents of said tar other than tar acids to effect selective vaporization of tar acids from the tar, passing admixed gas and vapors (including tar acid vapors) resulting from the treatment of the tar into contact with hot alkaline solution at substantially the same temperature as that at which the said tar and inert gas are contacted to absorb selectively the tar acid vapors, and recycling into contact with the tar inert gas and vapors unabsorbed by said alkaline solution.

9. The method of recovering tar acids from tar containing tar acids and neutral oil constituents which comprises heating said tar to a temperature above its initial boiling point, continuously introducing the resultant heated liquid and vapors evolved therefrom into intimate contact with a stream of inert gas containing vapors of said neutral oil constituents and intimately contacting said heated liquid with said stream of inert gas to vaporize tar acids from the heated liquid, continuously passing the resulting gases and vapors (including tar acid vapors) into contact with a hot alkaline solution at a temperature at which the tar acid vapors are selectively removed from the gases and vapors, and recycling inert gas containing neutral oil vapors unabsorbed by said hot alkaline solution into contact with said tar.

10. The method of recovering tar acids from tar containing tar acids and neutral oil constituents which comprises heating said tar to a temperature above its initial boiling point, continuously introducing the resultant heated liquid and vapors evolved therefrom into intimate contact with a stream of inert gas containing vapors of said neutral oil constituents and intimately contacting said heated liquid with said stream of h' inert gas to vaporize tar acids from the heated liquid, continuously passing the resulting gases and vapors (including tar acid vapors) into contact with a hot alkaline solution at a temperature at which the tar acid vapors are selectively removed from the gases and vapors Without removal of vapors of other constituents of the tar in amount in excess of that soluble in the carbolate solution resulting from the absorption of the tar acid vapors in said hot alkaline solution, and recycling inert gas containing neutral oil -vapors unabsorbed by said hot alkaline solution into contact with said tar.

11. rlhe method of recovering tar acids from tar containing tar acids and neutral oil constituents Which comprises heating said tar to a temperature of about 125 C. or higher and above itsinitial boiling point, continuously introducing the resultant heated liquid and vapors evolved therefrom into intimate contact with a stream of inert gas containing vapors of said neutral oil constituents and intimately contacting said heated liquid With said stream of inert gas to vaporize tar acids from the heated liquid, continuously passing the resulting gases and vapors (including tar acid vapors) into contact With a hot alkaline solution at a temperature at which the tar acid vapors are selectively removed from the gases and vapors Without removal of vapors of other constituents of the tar in amount in excess of that soluble in the carbolate solution resulting from the absorption of the tar acid vapors in said hot alkaline solution, and recycling inert gas containing neutral oil vapors unabsorbed by said hot alkaline solution into contact with said tar.

l2. The method of recovering tar acids from tar containing tar acids and neutral oil constituents which comprises heating said tar to a temperature of about 125 C. or' higher and above its initial boiling point, continuously introducing the resultant heated liquid and vapors evolved therefrom into intimate contact With a stream of inertv gas containing vapors of said neutral oil constituents and intimately contacting said heated liquid With said stream of inert gas to vaporize tar acids from the heated liquid, continuously passing the resulting gases and vapors (including tar acids vapors) into contact With a hot alkaline solution at a temperature of about 120 C. or higher at which the tar acid vapors are selectively removed from the gases and vapors Without removal of vapors of other constituents of the tar in amount in excess of that soluble in the carbolate solution resulting from the absorption oi the tar acid vapors in said hot alkaline solution, and recycling inert gas containing neutral cil vapors unabsorbed by said hot alkaline solution into Contact With said tar.

13. The method of selectively recovering tar acids from hydrocarbon materials containing the same which comprises selectively distilling tar from a hydrocarbon material containing said tar acids While repressing distillation of hydrocarbon therefrom by bringing said hydrocarbon material and an inert gas containing vapors of constituents of said hydrocarbon material other than tar acids into intimate contact with each other at a tempera-ture of about 125 C. or higher to effect selective vaporization of tar acids from the hydrocarbon material, and passing admixed bolate solution resulting from the absorption of the tar acid vapors in said hot alkaline solution.

14. The method of selectively recovering tar acids from hydrocarbon materials containing the same which comprises selectively distilling tar acids from a hydrocarbon material containing said tar acids While repressing distillation of hydrocarbons therefrom by contacting said hydrocarbon material at a temperature of about 125 C. or higher With inert gas containing vapors of constituents of said hydrocarbon material other than tar acids to effect selective vaporization of tar acids from the hydrocarbon material, and passing admixed gas and vapors (including tar acid vapors) resulting from the treatment of the hydrocarbon material into contact With a hot alkaline solution at a temperature of about C. or higher to absorb selectively the tar acid vapors.

15. The method of simultaneously dehydrating and dephenolizing wet tar containing tar acids and neutral oil constituents Which comprises preheating said wet tar to a temperature above its initial boiling point to convert the Water contained in the tar into steam, continuously introducing the resultant heated liquid and vapors evolved therefrom into intimate contact with a stream of inert gas containing vapors of said neutral oil constituents and intimately contacting said heated liquid with said stream of inert gas to vapcrize tar acids from the heated liquid, continuously circulating gases and vapors (including tar acid vapors) resulting from the aforedescribed preheating of the tar and contact of the preheated tar with said stream of inert gas into contact with a hot alkaline solution at a temperature at which the tar acid vapors are selectively removed from the gases and vapors, circulating inert gas containing neutral oil vapors unabsorbed by said hot alkaline solution into` contact with said tar and continuously withdrawing from the thus circulated gases and neutral oil vapors the excess thereof.

16. The method of distilling tar, which comprises heating tar above the boiling point of its lower boiling constituents, flashing the tar, vaporizing tar acids from the resulting ho-t residue thereby obtained in a current of inert gases including neutral oil vapors, passing the resulting gases and vapors together with vapo-rs from the flashing operation through a cycle which includes bringing them into direct contact with an alkaline reagent to remove tar acids therefrom and bringing at least a portion of the resulting neutral oil vapors back into contact with the residue from the flashing operation.

1'7. The methof of distilling tar, which comprises heating tar above its initial boiling point, flashing the heated tar thereby separating vapors from undistilled residue and selectively Vaporizing tar acids from the hot residue thereby obtained in a current of inert gases including neutral oil vapors.

18. The method of distilling tar, Which comprises heating tar above its initial boiling point, flashing the tar to separate vapors from undistilled residue, distilling tar acids from the undistilled hot residue thereby obtained in a current of inert gases including neutral oil vapors, extracting tar acids from the resulting gases and vapors by direct contact with an alkaline reagent, dividing the resulting gases and vapors into two parts and returning one part into Contact with the residue from the flashing operation.

STUART PARMELEE MILLER. 

